1. Trachelate (Trachelatum). When of itself it forms a neck, the prothorax being represented only by membrane.—Ex. Xiphydria.
2. Unarmed (Inerme). When it has no prosternum.—Ex. The Rhyncophorous beetles. 3. Armed (Armatum). When it has a prosternum. N.B. These two last terms may be extended also to the Medipectus and Postpectus. And also to the whole together. Thus, if there was no Sternum at all, it should be called Pectus inerme; and if one existed in all these divisions of the breast, it would be Pectus armatum.
c. arm (Brachium).
α. cubit (Cubitus).
1. Clypeate (Clypeatus). When a concavo-convex plate is affixed to the outside of the cubit.—Ex. Crabro clypeatus, scutatus, &c. ♂. Plate [XV]. Fig. 3. a.
2. Palmate (Palmatus). When towards the apex the cubit is armed laterally with several divaricate spiniform teeth.—Ex. Scarites, Clivina. Plate [XV]. Fig. 5.
3. Digitate (Digitatus). When the apex of the cubit is divided into several long teeth or fingers.—Ex. Gryllotalpa. Plate [XV]. Fig. 6.
4. Dolabrate (Dolabratus). When the apex of the cubit is dilated and shaped something like the head of a hatchet. Plate [XV]. Fig. 4.
β. hand (Manus).
1. Patellate (Patellata). When several joints of the hand are dilated so as to form an orbicular patella furnished underneath either with suckers, or a dense brush of hairs.—Ex. Dytiscus ♂, Staphylinus. Plate [XV]. Fig. 9.
2. Scutate (Scutata). When a single joint of the hand is dilated into a broad scutiform plate.—Ex. Hydrophilus piceus ♂. Plate [XV]. Fig. 8.
3. Strigilate (Strigilata). When on the inner side of the first joint of the hand or palm the segment of a circle is taken out at the base opposite to the spur, the sinus being often pectinated with spines.—Ex. Apis[1101]. Plate [XXVII]. Fig. 36. a.
4. Auriculate (Auriculata). When any of the joints are externally dilated into an auriform process.—Ex. Gryllotalpa. Plate [XV]. Fig. 6. t´´.
ii. ALITRUNK (alitruncus).
1. Buried (Sepultus). When its upper surface is wholly or nearly covered and hidden by the thorax, elytra or other organs of flight[1102].—Ex. Coleoptera, Orthoptera.
2. Revealed (Revelatus). When it is not so covered, but is equally conspicuous with the Prothorax, or even more so.—Ex. Neuroptera, Hymenoptera, Diptera. Atractocerus in Coleoptera.
3. Coalite (Coalitus). When it is not separable into two segments, the Medipectus and the Postpectus forming one piece.—Ex. Cimex L.
4. Bisected (Bisectus). When it is separable into two segments.—Ex. Lamellicorn beetles.
a. mesothorax.
α. collar (Collare).